Abstract
The Danish Pesticide Leaching Assessment Programme (PLAP) was initiated in 1998 by the Danish Parliament in order to evaluate whether the use of approved pesticides will result in an unacceptable contamination of the groundwater, if applied under field conditions in accordance with current Danish regulation. In this programme, water samples from variably saturated soil and groundwater collected at five cultivated fields are analysed for selected pesticides and their degradation products. The PLAP results are summarised and evaluated in yearly reports and used by the Danish Environmental Protection Agency in the regulation of pesticides in Denmark (Brüsch et al. 2015). In order to represent typical farming scenarios in Denmark, the test fields are situated on meltwater and marine sands, and on tile-drained clayey soils in till areas.
Highlights
MethodsThe five cultivated Pesticide Leaching Assessment Programme (PLAP) fields (1.2–2.4 ha), representing different soils and hydrogeological settings, spread across Denmark (Fig. 1) are located at Silstrup, Estrup and Faardrup with tile-drained clayey soils, and at Tylstrup and Jyndevad with sandy soils (Lindhardt et al 2001)
The Danish Pesticide Leaching Assessment Programme (PLAP) was initiated in 1998 by the Danish Parliament in order to evaluate whether the use of approved pesticides will result in an unacceptable contamination of the groundwater, if applied under field conditions in accordance with current Danish regulation
The PLAP fields are farmed according to conventional agricultural practice, and pesticides are applied in the maximum permissible doses and as specified in the regulations
Summary
The five cultivated PLAP fields (1.2–2.4 ha), representing different soils and hydrogeological settings, spread across Denmark (Fig. 1) are located at Silstrup, Estrup and Faardrup with tile-drained clayey soils, and at Tylstrup and Jyndevad with sandy soils (Lindhardt et al 2001). Water samples are collected weekly from drainage at the clayey till fields, and monthly from standard teflon suction cups in the unsaturated zone at the sandy fields, and from horizontal and vertical groundwater monitoring wells at all fields. The horizontal wells are installed at the clayey till fields at depths of 2–3.5 m under the pesticide-treated areas, and at the sandy fields just beneath the fluctuating groundwater table. Detection of pesticides or their degradation products can be directly related to the specific pesticide application to the PLAP fields by monitoring both the variably and fully saturated soil and accounting for potential upstream influx. In the two sandy soils, the weighted average pesticide concentration leached to the suction cups at 1 m depth is estimated from the detected concentrations and estimated percolation on a monthly basis (Brüsch et al 2015). Precipitation (mm/y)* Potential evapotranspiration (mm/y)* Area (ha) Tile drain Depth to tile drain (m) Deposited by Sediment type Topsoil classification
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